Various film formation processes, such as a vacuum vapor deposition process, a sputtering process and an ion plating process, have been developed. A laminate obtained by such a film formation process is widely utilized in production of display devices, such as liquid crystal displays or organic LE (Light Emitting) displays, semiconductor devices, etc. In the display devices, the semiconductor devices, etc., the laminate is usable as a protective film, and various types of functional films, such as an optical filter and an anti-reflection film.
Late years, demand for device units using the functional films, such as a LCD (Liquid Crystal Display) TV, a mobile phone and a video game machine, has been rapidly expanded. Along with expansion of the demand, it has become an urgent matter to develop a technique for mass-producing a functional film within a short period of time. In order to respond to this need, a roll-to-roll technique has been developed. The roll-to-roll technique is designed to unroll and feed an elongated substrate wound in a roll form, between two rolls, so as to enable continuous film formation, thereby increasing efficiency of a film formation operation.
One example of a film formation method using a roll-to-roll technique is disclosed in JP 4415584B (Patent Document 1). In this film formation method, one rotary drum is provided between two rolls, and a plurality of targets are arranged with respect to the one rotary drum which is transporting a substrate, to enable continuous film formation, thereby increasing efficiency of the film formation operation.
JP 2010-236076A (Patent Document 2) and JP 07-098854A (Patent Document 3) disclose a film formation method capable of subjecting particularly both sides of a substrate to film formation, using the roll-to-roll technique. In this film formation method, with a view to enabling double-side film formation, two rotary drums and one take-up roll disposed between the rotary drums are used, wherein a substrate fed from a feed roll is subjected to film formation through the two rotary drums which are rotating in respective opposite directions, and then rolled up on the take-up roll.